1. Field of the Invention
The present invention relates to an improvement in a belt conveyor that includes protrusions formed on a conveyor belt and holes formed on a pulley that mesh the protrusions.
2. Prior Art
FIG. 6 shows one type of belt conveyor system. In this system, an elongated protrusion 2xe2x80x2 is formed on the back surface of a conveyor belt 1xe2x80x2 so as to extend in the belt running direction, and this elongated protrusion 2xe2x80x2 fits in a peripheral groove 4xe2x80x2 formed in the periphery of the pulley 3xe2x80x2. This system is disclosed in, for instance, Japanese Utility Model Application Laid-Open (Kokai) No. H3-56712.
This belt conveyor prevents the conveyor belt 1xe2x80x2 from meandering thanks to the engagement of the protrusion and the groove. However, the engagement between the protrusions and the groove does not transmit the driving force of the pulley to the belt.
Other types of belt conveyors are shown in FIGS. 7 and 8. In FIG. 7, teeth 6xe2x80x2 are formed on the back of the conveyor belt 5xe2x80x2, and these teeth 6xe2x80x2 are meshed with teeth 8xe2x80x2 formed in the periphery of the pulley 7xe2x80x2. In FIG. 8, a cogged belt 10xe2x80x2 is attached to one side of the conveyor belt 9xe2x80x2 and a flanged wheel 12xe2x80x2 is mounted on one side of the pulley 11xe2x80x2 so that the cogs of the belt and the flanges of the wheel mesh each other. This conveyor is disclosed in, for instance, Japanese Patent Application Laid-Open (Kokai) No. H9-124123.
In these belt conveyors, the conveyor belt 5xe2x80x2 (FIG. 7) and the conveyor belt 9xe2x80x2 (FIG. 8) which is equipped with the cogged belt 10xe2x80x2 are respectively used as a timing belt; and the pulley 7xe2x80x2 (FIG. 7) and the pulley 11xe2x80x2 which is equipped with the flanged wheel 12xe2x80x2 (FIG. 8) are respectively used as a timing pulley.
In all of these prior arts, the cross sectional shape of the teeth is trapezoid. Because of this shape, when the driving-force-transmission power weakens or when the belt is stretched out, the belt tension becomes weak. When this happens, the belt tension needs to be adjusted.
The biggest problem with these belt conveyors is that different types of belts are required for different types of belt conveyors. For example, the belt 5xe2x80x2 in FIG. 7 and the belts in FIG. 8 are all different. Also, the belt having teeth that mesh the teeth of a timing belt formed at the center of a pulley (see FIG. 7) and the belt having teeth for meshing the teeth of a timing belt formed at both ends of a pulley (not shown) are different.
In view of the above, the first object of the present invention is to provide a conveyor belt that is free from meandering and does not require adjustment of belt tension. Another object of the present invention is to facilitate the manufacture of a driving roller and to make it possible to use a common belt for different types of conveyors.
To accomplish the first object, in the present invention, each of the protrusions formed on the back surface of a conveyor belt comprises inwardly curved front and rear sides thus tapering towards the top, and the periphery of a pulley is formed with holes that are shaped so as to fit the protrusions.
With this structure, the peculiarly shaped protrusions of the conveyor belt and the holes of the pulley that are shaped so as to fit the protrusions drive the conveyor when they mesh with each other, thus preventing the conveyor belt from meandering. Since the protrusions of the belt and the holes of the pulley are constantly meshed with each other, the belt tension is constant at all times, eliminating the need for tension adjustment.
Preferably, the pulley is a separate unit from and is detachable from the roller. As a result, the pulley and the roller can be manufactured independently, and the pulley can be easily attached to the roller. Moreover, the holes of the pulley can be made by pressing (burring), so that the manufacturing process of components is easy.
The conveyor belt, which has a fixed width and the protrusions thereon, may be used alone. Instead, such a belt having the protrusions can be fastened at a certain position on the back surface of a flat (wide) belt.
In other words, a conveyor for carrying goods can be easily composed using the fixed width conveyor(s). By fastening the fixed width conveyor belt(s) at a certain position(s) on the back surface of a flat (wide) belt, it is possible to use same type of flat belts for rollers having pulleys at different locations. For instance, for a roller with pulleys mounted at both ends thereof, fixed width belts are provided on both edges of a flat belt; and for a roller with a pulley at its center, a single fixed width belt is provided at the center of a flat belt. In either case, since the conveyor belts have the same fixed width, the fixed width conveyor belts can be fastened at appropriate locations (edges or center, for instance) on the back surface of the flat belts of the same type. Thus, the same type of flat belts can be commonly used for rollers having pulleys at different locations.